Lithium electric cells with novel positive active materials and non-aqueous electrolyte

ABSTRACT

Electric cells of high energy density with lithium negative electrodes, substantially insoluble positive active materials selected from the group of argentous chromate and lead chromate and a non-aqueous electrolyte which is a molar or 1.5 molar solution of lithium perchlorate in a solvent selected from the group consisting of tetrahydrofuran-propylene carbonate, methylformatepropylene carbonate, tetrahydrofuran-dimethyl carbonate, tetrahydrofuran-dimethoxyethane-propylene carbonate, tetrahydrofurandimethoxyethane, and tetrahydrofurandimethoxyethane-propylene carbonate.

United States Patent Lehmann et all.

Jan. 14,1971

LITHIUM ELECTRIC CELLS WITH NOVEL POSITIVE ACTIVE MATERIALS ANDNON-AQUEOUS ELECTROLYTE Inventors: Gerard Lehmann; Jean-Paul Gabano,both of Poitiers, France Societe des Accumulateurs Fixes et de Traction(Societe Anonyme), Romainville, France Filed: Apr. 27, 1971 Appl. No.2137,845

Assignee:

Foreign Application Priority Data France 71.01175 References CitedUNITED STATES PATENTS 10/1951 Ruben.....

l/1957 Shorr 136/137 2,967,898 1/1961 Ruben 136/119 3,189,485 6/1965Panzer 136/93 3,310,436 3/1967 Ralston et a1 136/137 X 3,468,708 9/1969Davis et al........ 136/137 X 3,511,716 5/1970 Gabano et a1 136/100 R3,658,592 4/1972 Dey 136/6 3,681,143 8/1972 Dey 136/83 R PrimaryExaminerAnthony Ska'pars Attorney, Agent, or Firm---Kenyon & KenyonReilly Carr & Chapin [57] ABSTRACT Electric cells of high energy densitywith lithium negative electrodes, substantially insoluble positiveactive materials selected from the group of argentous chromate and leadchromate and a non-aqueous electrolyte which is a molar or 1.5 molarsolution of lithium perchlorate in a solvent selected from the groupconsisting of tetrahydrofuran-propylene carbonate,methylformatepropylene carbonate, tetrahydrofurandimethyl carbonate,tetrahydrofuran-dimethoxyethane-propylene carbonate,tetrahydrofurandimethoxyethane, andtetrahydrofuran-dimethoxyethanepropylene carbonate.

7 11 Claims, 5 Drawing Figures PAIENTEL SEC 1 0 I974 SHEET 2 OF 3INVENTORS GERARD LEHMANN JEAN- PAUL GABANO BY f firormzvs PATENTED DEC 101974 sum 3 or 3 m o h S l 1 0 A INVENTOR GERARD LEHMANN JEAN-PAULGABANO BY 7 7 ATTORN YS LITHIUM ELECTRIC CELLS WITH NOVEL PDSllTllVEACTIVE MATERIALS AND NON-AQUEOUS ELECTROLYTE BACKGROUND OF INVENTIONvoltage level whereas, for example, the basic chromate Ag CrO isdischarged at two voltage levels. As already mentioned, argentouschromate and lead chromate are very insoluble compounds by themselves.Moreover,

5 they do not form any soluble complex during discharge.

This invention relates to electric cells with non- Lastlyto be "Q thatoxldlzlng Properties of aquegus electrolytes, f h type comprising a lihi CrO are not used in the electrochemical reaction. negative electrodeGood results have also been obtained with electro- In the presentlyknown cells f this type thg positive lytes comprising other solventsthan the hcreabove active material is generally constituted by coppersull mehhmed fide, silver chloride, copper chloride, silver oxide and h"bled feature Pf thls f F less advantageously mercuric chloride electriccell of the type comprising a lithium negative The electrolyte maybepreferably a molar solution of electrqde the poslhve active 'f bemgmamly lithium perchlorate in a mixture of tetrahydrofuran and ihorhpnsedof a chromate Selected from the group L2 dimethoxyethane l5 sisting ofargentous chromate and lead chromate,

In such a cell the positive active material must be as wheremElectrolyte Solvent ls Selected from the insoluble as possible so thatits transport towards the group g g of groptylene g i E f l negativeelectrode in the dissolved state is prevented. uran y Car Ona an mlx 0 6Ya Researches have been carried out with the object of drofurahpropylehecarbonate methylfmmate propy' finding new positive active materialswhich can be used lehe Carbonate tetrh'hydrohlrah dlmethyl carbonate insuch a cell, are insoluble in the electrolyte and protetrahydrofurahdlmethqxyethane propylene carbon vide Suitable energy ate andtetrahydrofuran-dlmethoxyethane.

Principal objects and features of the present inven Advahtageouhy theele ctmlyte ehher a molar or tion are an electric cell with anon-aqueous electrolyte, mhlar Soluhon of hthum f l more espe' of thetype Comprising a lithium negative elgctmdea cially if the electrolytesolvent is a mixture tetrahywherein the positive active material issubstantially indrofurandlmethyl carbonatesoluble in the electrolytewhile providing suitable enthe Case f the abQve-memmed mlxtures, theergy. It mainly comprises a chromate selected from the lQWmg PTOPOYUOYISy Volume) y be used group consisting of argentous chromate and leadchromate which have been found to meet these require emhydmfumh (THF) 70propylene carbonate (PC) 30 memstetrahydrofuran (Tl-IF) 20 dimethylcarbonate (DMC) 80 Argentous chromate, Ag CrO and lead chromate P py gga e (5) l g g gs e (M R 50 PbCrO, are more especially advantageous inthat they propylene tetr y m Eg are particularly insoluble in theabove-mentioned electhoxyethane (DME) 24 Y trolyte, which is a molar of1.5 molar solution of lithlehahydmhm" (THF) 70 dmethoxyethme (DME) 30ium perchlorate in a mixture of tetrahydrofuran and di Results relatingto the conductivity of the electrolytes methoxyethane. The solubilityhas been found in pracaccording to the invention and the solubility ofargentice to be 260 mg/l for argentous chromate and even tous chromatein such electrolytes have been gathered less for lead chromate whereasfor example, silver chlo- 40 in Table 1.

TABLE 1 No. Electrolyte Conductivity Solubility Ag Cr (ohm y l0 O,(Mg/lin Ag) 1 PC. Li Cl 0, lM 4,85 15 2 THF, Li Cl 0, IM 3 0 3 DMC, Li Cl 0,IM 5 I06 4 PC-MF (/50 in vol.),

Li Cl 0,1M IS 36 THF-PC (/30).

Li Cl 0, IM 9.5 35 e THF-DME-PC (56/24/20),

, Li Cl 0, [M 8.9 100 7 THF-DMC (/20) Li Cl 0, 1.5 M 4.90 8 THF-DMC(26/80) ride and argentic oxide are found to have respectivesolubilities of 439 and 535 mg/l. The capacity per unit of volume of theargentous chromate-lithium system is about 627 ampere-hours per dm" andits energy per unit of volume is about 2,000 watts-hours per dm. The 60capacity per unit volume of lead chromate is 695 Ah/dm and its energy isabout 2,160 Wh per dm. It may be seen that such systems are veryinteresting particularly for producing miniature cells of high voltageand low discharge rate.

They are all the more interesting as either argentous chromate or leadchromate are discharged at only one Li Cl 0 L5 M Tests have been made atthe boiling temperature of the said solvents. The results obtained forthe PC-MF (No. 4 above) and PC-THF (No. 3 above) mixtures are asfollows:

TABLE 2-Continued Vol. PC Vol. MF Boiling Temp. C

DRAWINGS FIG. 3 shows a graph which shows the discharge of a similarcell across a 62,000 ohm resistor;

FIG. 4 is a graph which shows a polarization curve of a system usinglead chromate as positive active material; and

FIG. 5 is a graph which shows polarization curves of systems accordingto the invention using argentous chromate as postive active material andelectrolyte with various solvents all according to the invention.

DETAILED DESCRIPTION Miniature sealed ce lls o t very small size havebeen made according to the invention and may, for instance, be used inwatches.

The structure of such cells is shown in FIG. 1 of the annexed drawings.

As may be seen in FIG. I, the cell C is of the button type comprising ametallic bottom cup and a metallic cover 11, both, for example, ofstamped nickel plated steel. The cathode 12 is mainly made of argentouschromate according to the invention. It is a mixture of 99 percentargentous chromate and 1 percent carbon black (or any other materialensuring a good electrical conductivity of the electrode). This mixtureis directly pressed into cup 10 and is held in place as by ring 13,made. e.g., of stamped steel.

The anode I4 is a lithium disk. A grid 15 made of nickel plated steel,or stainless steel. is welded to cover 11 of the cell and is embedded inthis disk 14. This ensures both good cohesion and good electricalcontact.

The separator bears reference 16. It may be constituted by one orseveral layers of felted fibers unaltered by the electrolyte and theactive materials. Polypropylene can be advantageously used in contactwith the positive electrode or cathode I2 and cellulosic materials incontact with the negative electrode or anode I4.

Example I The non-aqueous electrolyte of cell C is constituted by alithium perchlorate solution in a solution ina solvent mixture oftetrahydrofuran and 1-2 dimethoxyethane. This solution may comprise 62percent by weight of tetrahydrofuran. 27 percent by weight ofdimethoxyethane and II percent of lithium perchlorate.

An electrically insulating gasket 17 ensures the sealing between thejoined bottom cup 10 and the cover 11 of the casing and also theelectrical insulation of those two parts which respectively constitutethe electric terminals of the cell.

Cells have been made with the following characteristics:

cathode I2: Ag CrO (99 percent) by weight plus carbon black (1 percentby weight): 750 mg, theoretical capacity 120 mAh. anode 14: lithium disk1.2 mm thick 8.4 mm diameter with an embedded stainless steel grid 15welded to the negative cover 11. electrolyte with the above-mentionedcomposition:

100 microliters in the cathode and 80 microliters in the anodecompartments. Total weight of the cell 1.7 g

Outer diameter l 1.2 mm

Total height 5.8 mm

Total volume of the cell 0.58 cm After a 24 hours rest, the cell Cdischarging across a 9,100 ohm resistor has given the following results:

average discharge voltage 2.95 volts discharge time 380 hrs (end voltage1.7v)

discharged capacity 120 mAh cathode efiiciency 10071 output energy 355mwh energy per unit of volume 615 wh/dm" internal resistance about I00ohms at half discharge Other tests have been made by discharging thecell across a 62,000 ohm resistor (discharge time: about 3 months). Ithas been found that after operating for about 1,200 hours. the cellvoltage was quite steady and equal to 3.15 volts These tests areillustrated by the curves of FIGS. 2 and 3 which represent the dischargevoltage plotted against the discharge time, voltage V in volts beingplotted as ordinates and time T as abscissae.

The curve of FIG. 2 illustrates the discharge across the 9,100 ohmresistor and that of FIG. 3 the discharge across the 62,000 ohmresistor.

Other cells have been made by substituting lead chromate for argentouschromate, and either propylene.car bonate or a mixture of (PC) propylenecarbonate 20 percent by volume tetrahydrofuran (TI-IF) 70 percent byvolume for the mixture of tetrahydrofurandimethoxyethane.

In such cells, the composition of the cathode material was as follows:lead chromate 99 percent and carbon black 1% both by weight. The opencircuit voltage was about 3.10 V. The average voltage of such a celldischarged through a 62,000 ohm resistor was 2.56 V with PC and 2.47 Vwith the mixture PC-TI-IF. Polarization curves of such a system wereobtained by galvanostatic The open circuit voltage was in all casesabout 3.2 volts.

Discharge tests of the cells with electrolytes 1-8 of Table 1 across a62,000 ohm resistor'at 30C. have been carried out; the following tablegives the average voltages obtained with such cells.

' TABLE 3 No. Electrolyte from table 1 Average voltage (in volts) Thepolarization curves of the various systems have been plotted bygalvanostatic sweeping at a rate of 4 mA per cm per hour. I

These curves arereproduced in FIG. 5. in FIG 5, the voltage V in volts,has been plotted as ordinates and the current density D in milliamperesper cm in abscissae. The reference numbers given to the curvescorrespond to the number of the electrolyte (table 1) used for eachminiature cell. These curves show that the systems according to theinvention, using argentous chromate as positive active material have arelatively high dischargeability and can bear without excessivepolarization discharges at relatively high current densities, as

compared to the usual rate used in watches to microamperes per cm').

It is to be understood that the invention is in no way limited to theembodiments which have been described and illustrated solely asexamples. More especially, it is possible to bring some modifications,change some dispositions or replace some means by equivalent meanswithin the scope of the appended claims without departing from thespirit of the invention.

What is claimed is l. Miniature electric cell with a nonaqueouselectrolyte, said cell being of the type comprising a lithium negativeelectrode and a positive electrode whose active material consists ofabout I percent by weight of carbon black as conductive material andabout 99 percent by weight of argentous chromate.

2. Miniature electric cell according to claim 1, wherein saidelectrolyte consists of a solution of lithium perchlorate in a solvent,said solvent being selected from the group consisting of polypropylenecarbonate,

tetrahydrofuran, dimethyl carbonate, mixtures of tetrahydrofurandimethoxyethane, tetrahydrofuran propylene carbonate, methylformatepropylene carbonate,

tetrahydrofuran dimethyl carbonate and tetrahydrofuran dimethoxyethanepropylene carbonate.

3. Electric cell according to claim 2 wherein the said solvent consistsby volume of percent tetrahydrofuran and 30 percent dimethoxyethane.

4; Electric cell according to claim 2 wherein the said solvent consistsby volume of about 50 percent of propylene carbonate and 50 percent ofmethylformate.

5. Electric cell according to claim 2 wherein the said solvent consistsof volume of about 70' percent tetrahydrofuran and 30 percent propylenecarbonate.

6. Electric cell according to claim 2 wherein the said solvent consistsby volume of 20 percent tetrahydrofuran and percent dimethyl carbonate.

7. Electric cell according to claim 2 wherein the said solvent consistsby volume of about 56 percent tetrahydrofuran, 24 percentdimethoxyethane and 20 percent propylene carbonate.

8. Electric cell according to claim 2 wherein the lithium perchloratesolution ranges from molar to 1.5 molar.

9. Sealed miniature cell comprising a cathode consisting by weight ofabout 1% carbon black and about 99% of argentous chromate as activematerial, an anode of lithium, a non-aqueous electrolyte consisting oflithium perchlorate solution in a-solvent selected from the groupconsisting of propylene carbonate, tetrahydrofuran, dimethyl carbonate,mixtures of tetrahydrofuran dimethoxyethane, tetrahydrofuran propylenecarbonate, methylformate propylene carbonate, tetrahydrofuran dimethylcarbonate and tetrahydrofuran dimethoxyethane propylene carbonate, aseparator comprised of layers of'felted fibers unaltered by theelectrolyte and the said active material, a casing comprising a metallicbottom cup into which said cathode is deposited and a metallic cover,said bottom cup and the cover constituting the respective terminals ofthe cell and being in direct electrical contact respectively with thecathode and the anode and an insulating gasket separating said cup andcover. 10. Miniature cell according to claim 9 wherein a non-corrodinggrid is embedded in the lithium disk constituting the anode, and weldedto said cover constituting the negative terminal.

11. Minature cell according to claim 10 wherein grid is of stainlesssteel.

said

UNITED STATES PATENT oEEEEE EIHCATE M CQEQTWN Patent N D d December 10 lGerard Lehmann and Jean-Paul Gabano It is certified that error appearsin the above-identified patent and that said Letters Patent are hengbycorrected as shown below:

In Item 30 of the title page of this patent "Foreign ApplicationPriority Data" should read:

---October 29, 1970 France 70 39 1A0 ----=-January 1 1971 France 71 O1175 -a Signe and ficaled this twenty-ninth 9.) 0? July 1975 [SEAL] Attes t:

RUTH C. MASON C. MARSHALL DANN AINS I'HX ()ffI'CPr (ummissiuner oflatcmsand Trademark-x F ORM PO-105O (10-69) USCOMM-DC 60378-P69 u 5.GOVERNMENT PRINTING orncs: 930

1. MINIATURE ELECTRIC CELL WITH A NONAQUEOUS ELECTROLYTE, SAID ELL BEINGOF THE TYPE COMPRISING A LITHIUM NEGATIVE ELECTRODE AND A POSITIVEELECTRODE WHOSE ACTIVE MATERIAL CONSISTS OF ABOUT 1 PERCENT BY WEIGHT OFCARBON BLACK AS CONDUCTIVE MATERIAL AND ABOUT 99 PERCENT BY WEIGHT OFARGENTOUS CHROMATE.
 2. Miniature electric cell according to claim 1,wherein said electrolyte consists of a solution of lithium perchloratein a solvent, said solvent being selected from the group consisting ofpolypropylene carbonate, tetrahydrofuran, dimethyl carbonate, mixturesof tetrahydrofuran - dimethoxyethane, tetrahydrofuran -propylenecarbonate, methylformate - propylene carbonate, tetrahydrofuran -dimethyl carbonate and tetrahydrofuran -dimethoxyethane - propylenecarbonate.
 3. Electric cell according to claim 2 wherein the saidsolvent consists by volume of 70 percent tetrahydrofuran and 30 percentdimethoxyethane.
 4. Electric cell according to claim 2 wherein the saidsolvent consists by volume of about 50 percent of propylene carbonateand 50 percent of methylformate.
 5. Electric cell according to claim 2wherein the said solvent consists of volume of about 70 percenttetrahydrofuran and 30 percent propylene carbonate.
 6. Electric cellaccording to claim 2 wherein the said solvent consists by volume of 20PERCENT tetrahydrofuran and 80 percent dimethyl carbonate.
 7. Electriccell according to claim 2 wherein the said solvent consists by volume ofabout 56 percent tetrahydrofuran, 24 percent dimethoxyethane and 20percent propylene carbonate.
 8. Electric cell according to claim 2wherein the lithium perchlorate solution ranges from molar to 1.5 molar.9. Sealed miniature cell comprising a cathode consisting by weight ofabout 1% carbon black and about 99% of argentous chromate as activematerial, an anode of lithium, a non-aqueous electrolyte consisting oflithium perchlorate solution in a solvent selected from the groupconsisting of propylene carbonate, tetrahydrofuran, dimethyl carbonate,mixtures of tetrahydrofuran - dimethoxyethane, tetrahydrofuran -propylene carbonate, methylformate - propylene carbonate,tetrahydrofuran -dimethyl carbonate and tetrahydrofuran -dimethoxyethane -propylene carbonate, a separator comprised of layers offelted fibers unaltered by the electrolyte and the said active material,a casing comprising a matallic bottom cup into which said cathode isdeposited and a metallic cover, said bottom cup and the coverconstituting the respective terminals of the cell and being in directelectrical contact respectively with the cathode and the anode and aninsulating gasket separating said cup and cover.
 10. Miniature cellaccording to claim 9 wherein a non-corroding grid is embedded in thelithium disk constituting the anode, and welded to said coverconstituting the negative terminal.
 11. Minature cell according to claim10 wherein said grid is of stainless steel.